Materials of animal origin

Animals are mainly herbivores. Certain species, such as cows, can digest carbohydrate cellulose and change it into nutrients. Humans are mainly dependent on an intake of carbohydrates in the form of sugar and starch, but also need protein, carbohydrate, vitamins, minerals, etc.

Humans and animals depend entirely on air for respiration. Oxygen enriches the blood and makes the body capable of burning food in an exothermic reaction releasing heat, approximately 80-150 W for an adult human being, depending upon the level of activity.

Associated with the very ancient constructions is the use of animal products such as hides and sinews for fastening and cladding. There was also the bizarre use of animal (mammoth) bones as a structural material on the steppes of Eastern and Northern Europe. Animal glue is the oldest type of glue known, and was used in ancient Egypt. In later times, animal products have played only a minor role, such as blood and cow manure added as binding agents in earth constructions and wall renderings.

Yet products from the animal world still have a limited use in modern building. Sheep's wool is common in carpets, wallpapers and building paper products. Wool of lower quality, which would otherwise be wasted, can be used for insulation and joint sealing. The substance keratin, which strengthens plant fibre products, can be extracted from wool as well as from feathers (Kawahara et al., 2004). Beeswax has become a popular substance for treating timber surfaces.

Protein substances extracted from milk, blood or tissues are still used as binding agents for paint and glue. Traditional animal glue is produced by boiling skin and bone to a brown substance. When it is cleaned, gelatine, which is also a useful base for bioplastics, is obtained. Casein glue is made from milk casein, produced from curdled milk by adding rennet. Casein contains more than 20 different amino acids and is a very complex chemical substance, but has no binding power in itself. Lime or other alkalis must be added and the mixture is dissolved in water, see page 263. Casein plastic CS is produced from milk casein by heating the casein molecules with formaldehyde under pressure. This plastic, also called synthetic bone, is sometimes used for door handles.

Adding whey can improve the fire resistance of insulation materials by producing nitrogen under intense heat. When lactic sugar ferments,

iTable 11.1 Building materials from the animal kingdom

Species

Part used

Areas of use

Mussels

Shell

Aggregate in concretes and mortars, thermal insulation, capillary barriers

Coral

Mineral part

Building blocks, structures

Bees

Wax

Surface treatment of wood

Skeleton

Bioplastics (via chitin)

Shellfish

Skeleton

Bioplastics (via chitin)

Fish

Oil

Binder in paint and adhesives

Birds

Down

Strengthener in products of natural fibres (keratin)

Egg

Binder in paint and adhesives

Hoofed animals

Wool (sheep/goat)

Textiles, sheeting, joint sealing around doors and windows, thermal insulation, strengthener in products of natural fibres (keratin)

Hair (horse, pig, cow)

Reinforcement in clay plasters and mortars.

Hides and skins

Internal cladding, floor covering, binder in paint and adhesives (protein)

Bone tissue

Binder in paint and adhesives (protein), black pigment in paints (ash)

Blood

Binder in paint and adhesives (protein), water repellant and stabilizer in earth constructions

Milk

Binder in paint, adhesives and fillers (casein), flame retarder (whey), biocide (lactic acid), bioplastics (casein, lactic acid)

Manure

Stabilizer in earth constructions

lactic acid (C2H4OHCOOH), which is a mild disinfectant, is produced. It can also be polymerized to form one of the leading bioplastics, polylactic acid PLA.

Coral is already widely used as a building material in the Maldives and similar island communities. In the tropical oceans, a future can be envisaged in which living corals (which depend upon warm water for quick growth) could be used in manufacturing tailored building components. However, this has considerable moral implications - as toxins might have to be used to hinder growth and produce the right forms and dimensions.

Various shell materials are also of interest. The large quantities of shells discarded from mussel farms and similar production industries seem to be promising as an aggregate in mortars (Yoon et al., 2004). Roughly crushed mussel shells have also been used as heat insulation and capillary break under floors. Chitin, found in the skeletal tissue of marine crustaceans - shrimp, lobster and other shellfish - is also expected to become a future base for bioplastics (Stevens, 2002).

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